Type:
var 𐋀;
where the character before the semi-colon is U+102C0 (CARIAN LETTER G).
Equivalently, try:
eval("var \u{102C0};"); // (note that the escape sequence is expanded when evaluating the string)
I get the error:
SyntaxError: Invalid character '\u55296'
I expect: no error (because U+102C0 is a letter).
Note that the following code works as expected (no error):
var \u{102C0};